How to Calculate Weighted eCPM Across Ad Inventory

Understand the components

Weighted eCPM boils down to two totals: the monetised impressions that actually served ads and the net revenue you kept. Each inventory line must be normalised to those two concepts before aggregation.

• Ad requests: The opportunities an ad server or SDK attempted to fill. Requests anchor the volume side of the equation.
• Fill rate: The percentage of requests that returned a creative. Multiply requests by fill rate to get monetised impressions.
• Gross revenue: The amount reported by the demand partner before revenue share, platform fees, or taxes.
• Revenue share / rev-share: The percentage of gross revenue paid to partners. Subtract it to express net revenue in the currency you report upstream.

Using consistent lookback windows and currencies is non-negotiable. Convert international revenue before you blend it and align every data source to the same day-part (for example, UTC revenue with UTC impression counts) so the weighted eCPM reflects an apples-to-apples comparison.

Derive the weighted eCPM formula

Start by expressing monetised impressions and net revenue for each line i:

Monetised Impressions_i = Requests_i × (Fill Rate_i ÷ 100)

Net Revenue_i = Gross Revenue_i × (1 − Rev-Share_i ÷ 100)

After normalising every line, sum them and scale to a thousand-impression basis:

Weighted eCPM = (Σ Net Revenue_i ÷ Σ Monetised Impressions_i) × 1,000

The constant 1,000 keeps the result in CPM units. If total monetised impressions equal zero, the equation is undefined—an important guardrail when troubleshooting missing data in reporting pipelines.

Collect and reconcile the inputs

1. Export requests and fill: Pull requests and filled impressions from the ad server, SDK, or mediation layer. If the platform provides filled impressions directly, you can use that field in place of requests × fill.
2. Pull gross revenue: Use the revenue totals aligned to the same time zone. If you receive revenue in multiple currencies, convert them at the financial system’s official rate before combining.
3. Document rev-share splits: Note the percentage retained by each partner or reseller. Some dashboards report net revenue already; set the rev-share field to zero when that is the case.
4. Match line items: Ensure each row in your worksheet maps one-to-one between requests, fill, revenue, and rev-share. Duplicates or mismatched naming conventions can double-count impressions.
5. Audit with totals: Sum requests, impressions, and revenue separately and reconcile them to finance and ad ops reports. Discrepancies larger than rounding differences need resolution before you calculate.

When spreadsheets become unwieldy, port the totals into the Weighted eCPM Planner. It performs the arithmetic instantly while documenting the assumptions alongside examples and FAQs for your stakeholders.

Worked example with three supply lines

Suppose a publisher runs three primary revenue sources during the same week:

• Direct-sold display: 120,000 requests at 85% fill produce 102,000 monetised impressions. Gross revenue totals $1,800 with a 15% agency commission.
• Programmatic open auction: 80,000 requests at 70% fill produce 56,000 monetised impressions. Gross revenue is $1,900 with no rev-share deduction.
• Rewarded video SDK: 40,000 requests at 95% fill produce 38,000 monetised impressions. Gross revenue is $980 with a 10% platform fee.

Net revenue equals $1,530 + $1,900 + $882 = $4,312. Monetised impressions equal 102,000 + 56,000 + 38,000 = 196,000. Plugging these totals into the formula gives:

Weighted eCPM = (4,312 ÷ 196,000) × 1,000 = $22.00

Compare this $22.00 weighted eCPM to individual line-item eCPMs to spot outliers. Programmatic open auction yields $33.93 on its own, but the lower-yielding rewarded video inventory drags the blended rate toward $22.00. Without weighting, you could misinterpret the stack’s performance by averaging the three eCPMs and landing at $24.21—two dollars higher than reality.

Scenario testing for optimisation

Once the baseline is clear, experiment with how adjustments affect the blended rate:

• Change fill dynamics: Increasing rewarded video fill from 95% to 98% without changing revenue adds 1,200 monetised impressions. The blended eCPM slips slightly unless revenue scales proportionally.
• Alter rev-share terms: Negotiating the agency commission from 15% to 12% increases net revenue by $54 on the direct-sold line, boosting the weighted eCPM to $22.28.
• Shift demand weighting: Moving 10,000 requests from the open auction to a private marketplace with higher CPMs changes both monetised impressions and revenue. Run the before-and-after scenario through the calculator to quantify the uplift.

Use companion tools like the Social Media ROI Calculator or SERP Feature Click Share Calculator to connect funnel changes with impression availability before you recalculate weighted eCPM.

Embed the metric in revenue reporting

Weighted eCPM should not live in isolation. Tie it to other monetisation KPIs to maintain context:

• Compare to ARPU and RPM: If your customer lifetime value model relies on revenue per user, align the weighted eCPM with those figures to explain yield differences by geography or platform.
• Blend with ROAS and CAC: Teams buying traffic should evaluate whether the weighted eCPM of on-site ads offsets acquisition costs. The ROI Calculator can translate the eCPM uplift into project ROI.
• Share with finance: Weighted eCPM becomes a forecasting input when modelling quarterly revenue. Pair the metric with scenario planners such as the YouTube Ad Revenue Forecast to demonstrate the downstream impact of inventory strategy changes.

Document assumptions for every executive deck: currency conversions, viewability thresholds, and whether ad-blocked traffic was excluded. Transparency prevents debates about data lineage later.

Troubleshooting common pitfalls

• Mismatched time zones: If revenue uses PST and requests use UTC, the numerator and denominator represent different windows. Re-extract the data with matched time zones.
• Inconsistent rev-share rules: Some partners deduct payment processor fees before reporting revenue share. Confirm whether the percentage is applied to gross or net so you do not double-count deductions.
• Inventory saturation: A sudden jump in requests without a matching revenue increase can drag weighted eCPM downward. Check whether demand caps or frequency management are blocking monetisation.
• Outliers and invalid data: Extremely low or high fill rates may signal measurement errors. Validate with the ad server log-level data before presenting the weighted result.

Maintaining a calculation log—inputs, formulas, and the date produced—lets future audits rebuild your work. Export the state of the Weighted eCPM Planner or archive your spreadsheet with version control.

Next steps

Weighted eCPM converts siloed ad operations data into a metric executives can benchmark. Establish a repeatable workflow: validate the source data, run the calculation with the planner, and share the results alongside ROI, CAC, and forecasting dashboards. Over time you will spot seasonality, detect inventory cannibalisation earlier, and negotiate with partners using evidence rather than instinct.